AirHint found the following cheapest return flights from Seoul (GMP) to Singapore (SIN) in September 2025 (see full year).

Return flights

09 Sep - 16 Sep	Eastar Jet
06 Sep - 09 Sep	Eastar Jet
10 Sep - 17 Sep	Eastar Jet
08 Sep - 15 Sep	Jeju Air
07 Sep - 16 Sep	T'way Air
06 Sep - 10 Sep	T'way Air
08 Sep - 17 Sep	Eastar Jet
06 Sep - 15 Sep	Jeju Air
11 Sep - 14 Sep	China Eastern
09 Sep - 14 Sep	China Eastern
25 Sep - 02 Oct	Jeju Air
18 Sep - 04 Oct	Jeju Air
24 Sep - 01 Oct	Air Busan
19 Sep - 04 Oct	Jeju Air
26 Sep - 01 Oct	Jeju Air
27 Sep - 01 Oct	T'way Air
27 Sep - 03 Oct	Jeju Air
27 Sep - 04 Oct	Jeju Air
30 Sep - 03 Oct	Jeju Air
20 Sep - 04 Oct	Jeju Air

Also check the deals for one-way flights from Seoul to Singapore in September.

The deals are updated regularly. The prices may go up as tickets are purchased by other travellers. Only the cheapest flights are offered. Select a price to book and secure these cheap prices.

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Cheapest return flights from Seoul to Singapore in September from $229

Return flights